Conventional filter devices, used in fields such as the point-of-use filtration of chemicals used in semiconductor manufacturing, are of two types: disposable devices and cartridge filters.
Despite advances in the field, disposable devices typically have excessively large internal flow channels, which are larger than the equivalent inlet and outlet ports and/or tubing and piping leading to and from the device. These large flow channels result in unnecessary hold-up volume and increases in pressure drop, due to expansions and contractions in the fluid flow path. Pressure fluctuations caused by the expansions and contractions can cause bubbles in the fluid that is being filtered to come out of solution. Increased pressure drop is detrimental to fluid processes that are sensitive to outgassing. The higher pressure required results in more dissolved gas and a greater occurrence of outgassing. Outgassing relates directly to defects in end use. Furthermore, the large flow channels mean that there are more places for bubbles to become trapped or for bubble nucleation to occur. Also, a larger amount of hold-up volume causes the filter to take a longer amount of time to prime and flush to background particle levels before use.
Cartridge filters, by definition, are used within a housing and thus typically have large flow channels between the housing and the filter. Thus, they suffer from similar problems produced by unnecessary hold-up volume.
As examples of the prior art, U.S. Pat. No. 5,620,599 of Hopkins et al. discloses a cartridge filter in which a sleeve or cage occupies typically 80% of the volume between the filter and the housing; and U.S. Pat. No. 5,762,789 of de los Reyes et al. discloses a disposable filter with low dead volume, in which a sweeping flow action improves the flow pattern.
Given the high cost of the process fluids used in fields such as semiconductor manufacturing, such as photoresists, dielectrics, anti-reflectives and optical disc materials, and the need to avoid defects produced by bubbles and other causes, the reduction of filter hold-up volume and reduction of flush-up time are critical. Although there have been efforts to reduce hold-up volume and flush-up time, there is therefore an ongoing need to reduce hold-up volume and flush-up time without increasing the pressure drop across the filter.